64 



CTENOPHORA. 



from the point of the aboral processes of the body he "deutlich beobachtete, dass von hier sich baum- 

 artig verzweigte Gefasse gegen den Darmkanal erstrecken". If this proves to be correct; it is indeed 

 a most interesting feature, probably homologous to the proliferations from the meridional vessels of 

 Bathyctena Chuni (Moser). (Comp. p. 36, note). 



A very surprising feature of M. ovum is the strong development of its muscular system, as is 

 easily observed in the preserved specimens. (Comp. fig. 11). The infundibular canal is quite surrounded 

 by a thick layer of longitudinal muscles; at the level of the infundibulum they divide so as to pass 

 outside the diaphragm, continuing down along the outer side of the pharyngeal vessels (the inner side 

 of these vessels is close to the pharyngeal wall, not separated therefrom by a muscle layer). At the 

 level of the transverse, perradial vessels the longitudinal muscles must, evidently, be divided into four 

 groups, uniting again, two on each side, below the transverse vessel. It is only on sections, however, 

 that one can realize how exceptionally these mucsles are developed. As seen in fig. 12, representing a 

 transverse section of the infundibular canal, the muscles form a thick layer round the canal, the single 

 threads being arranged more or less distinctly in a feather-like way, as it is known e. g. in the earth- 

 worm. The single threads are rather thick, comma-shaped 

 in cross-section. The whole muscle-bundle appears to be 

 :'''',V/'/?.'- limited outwards by a fine membrane. The longitudinal 



,.■■' ' ,, ' __ijji muscles along the outer side of the pharyngeal vessels 



"' ' are arranged in a similar way, but the muscle threads 



are less numerous here. Between the pharynx and the 

 tentacle-bases there is a conspicuous network of anasto- 



Fig. 12. Transverse section of the infundibular canal mosing muscle-strands. Also these Smaller bundles appear 

 of Mertensia ovum. inf. c. infundibular canal; 1. m. Ion- . . , , . , , . , _,, 



gitudinal mu.scles; r. ni. radial muscles. ^/,. '" sections to be surrounded by a thm membrane. The 



same reticulum of muscle-bimdles is also seen in the 



aboral part of the animal, taking almost the appearance of ring-muscles over the muscle-bundle round 



the infundibular canal; in fact, I am not quite sure whether there are not real ring-muscles here. 



This strong development of the musculature is quite astonishing and, as far as hitherto known, 



quite unique in the Ctenophores. It would, indeed, be very interesting to have this species made the 



object of a close histological and anatomical study. It may be supposed that its nervous system will 



prove to be considerably more developed than usual among Ctenophores, judging from its muscular 



system. 



The very interesting observation of Mertens, that it uses its tentacles for attaching itself to 

 stones etc. on the bottom, when the sea is in motion through stormy weather, in order to avoid being 

 thrown ashore and crushed, may be recalled here. Likewise Mertens (p. 527) records it to possess 

 strong regenerative power. (Comp. below, sub. Bolina infundibuhmi). 



Several specimens were taken by the "Ingolf" at the stations 29 (65° 34' N. 54° 31' W.), 

 33 (67°57'N. 55° 3°' W.) and 34 (65° 17' N. 54°i7'W.); in the Journal of the Expedition it is ment- 

 ioned from station 32 (66° 35' N. 56° 38' W.), all these stations being in the Davis Strait. — On the 

 "Danmark" Expedition it was observed by Mr. Fr. Johansen in considerable numbers in the months 

 of August and September 1907 at "Danmarks Havn" (North-East Greenland, 76° 47' N. 18° 45' W.), the 



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